As booster devices in vehicle brake devices, there are one using a vacuum booster and another using a hydraulic pressure (oil pressure) booster. In the vacuum booster, the driving of a master piston is boosted by an air pressure in an assist chamber. In the hydraulic pressure booster, on the other hand, the driving of a master piston is boosted by an oil pressure (i.e., hydraulic pressure) in an assist chamber.
Further, in a vehicle brake device wherein a booster device varies the pressure generated in wheel cylinders, hydraulic pressure regulating means is provided between a master cylinder and the wheel cylinders. The hydraulic pressure regulating means performs an ABS (antilock control), a vehicle stability control, and a TCS (traction control).
Further, in a hybrid vehicle, the pressure in wheel cylinders is controlled so that an actual brake force being the sum of a regenerative brake force and a hydraulic brake force by the wheel cylinders becomes a target brake force set in correspondence to the operating force on a brake pedal. A vehicle brake control device is described in JP2009-286170A for example.
The pressure variation in the wheel cylinders can be performed by generating a pressure difference between the pressure in the wheel cylinders (wheel pressure) and the pressure in the master cylinder (mater pressure) by the use of, for example, a valve device adjustable in flow pass resistance and a pump. That is, the wheel pressure can be controlled to be higher than the master pressure by making the pump discharge the brake fluid on the master cylinder side with respect to the valve device toward the wheel cylinder side with respect to the valve device while the valve device controls the flow of brake fluid between the master cylinder and the wheel cylinders, and the wheel pressure can be controlled to substantially the same hydraulic pressure as the master pressure by making the valve device release the flow of brake fluid between the master cylinder and the wheel cylinders.